Metal roof structures typically comprise a series of parallel rarer beams extending across the building in one direction and purlin beams parallel to each other mounted on top of the rafters extending in a direction normal to the rafters. The purlins are off enjoined together by support bracing or straps for-extra support. Insulation material in long sheets is placed in the area between purlins. The sheets of insulation material can be laid along the length of the purlins or across the purlins in a direction normal to the purlins. Hard roofing material such as metal decking is then attached on top of the purlins over the insulation material. Because the hard roofing material comes in long sheets and the roofs generally have two sloped sections, it is customary to construct the roof along the width of the sloped section and then proceed along the length of the structure from one end to the other. The workers stand on the previously laid section of roof to construct the next section.
The insulation material must be supported between the purlins, and various methods of support have been used. Mounting straps or wire mesh that are attached to the purlins by forming a lattice have been used. This is referred to as banding. A sheet, typically made of vinyl and acting as a vapor barrier, is then rolled onto the lattice, and insulation material is placed between adjacent purlins and over the sheet. If the installation of the lattice is done from underneath the roof structure, scaffolding or lifting equipment is required.
Some systems dispense with the lattice and use the sheet itself to support the insulation material. The support sheet is draped from the adjacent purlins and the insulation material is placed on top of the support sheet. A carriage is used to aid in the dispensing of the support sheet. The carriage is positioned on top of the purlins and travels the length of the purlins during the roof construction. A roll of the support sheet material is mounted on the carriage and the support sheet is dispensed from the roll and placed on top of the purlins. As the carriage travels the length of the purlins the support sheet is draped across the purlins. However, the support sheet sags between the purlins and results in a small vertical height at the sides of the insulation cavity adjacent to the purlins, and results in a compression of the insulation material in that area. Clips that attach the sides of the support sheet to the purlins have been used to alleviate the problem of the sagging support sheet. However, installation of the dips increases costs and endangers the workers that lean over the edge of the uncompleted roof to attach the dips.
A platform extending from the carriage has been used to support the support sheet prior to the attachment of the hard roofing material. The platform is positioned between adjacent purlins and extends out from the carriage and in the direction towards the previously completed section of roof. The support sheet is dispensed from the carriage and rests on the platform while the insulation is placed on top of the support sheet. The hard roofing material is then attached to the purlins on top of the insulation. The platform, being attached to the carriage, is then moved out from underneath the completed section of roof as the carriage is moved, and the procedure is repeated to complete the roof. Because the purlin support bracing and straps are located between the sides of the purlins, the platform must be positioned near the top of the purlins so that the platform will not be obstructed by the bracing as the carriage moves. Thus, the support sheet is relatively flat across the tops of the purlins and does not hang down into the space between the purlins to fill out the entire insulation cavity. Insulation placed on top of the support sheet is then compressed when the hard roofing material is attached to the purlins.
It would be desirable to have a system for building a roof structure that is inexpensive, safe and simple to construct, and that provides for an insulation support system which enables the full thickness of the insulation material to be used.